Time-limit switch for electric-light installations



July l, 1930.

E. A. FAGERLUND ET Al." 1,769,126

TIME LIMIT SWITCH FOR ELECTRIC LIGHT INSTALLATIONS Filed March 20, 1929Hure v1-ogs:

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Patented July` l, 1930 UNITED STATES PATENT OFFICE ERIK ARTUR FAGEHBLUNDAND KARL EINAB RUPERT LFGREN, F STOCKHOLM, SWEDEN; SAID LOFGBEN ASSIGNORTO HUGO THEODOR TILLQUIST, OF STOCKHOLM,

SWEDEN TIME-LIMIT SWITCH FOB ELECTRIC-LIGHT INSTALLATIONS Applicationled March 20, 1929, Serial No. 348,390, and in Germany March 22, 1927.

limit switch, when subjected to the action ofv an electric heating coil,causes the contact of the heating circuit to be opened and the contactof the main circuit of the switch to be 0 closed. On the other hand,when the heat ceases to act on the thermostat, this will cause thecontacts to be operated in reverse order during the following coolingperiod. The heating action, which causes the contacts to be opened andclosed as stated above, must take place very quickly, but the coolingand the opening of the main circuit caused thereby, should requireconsiderable time, this being an object, for which the thermostat is 0suitably designed.

The invention relates to improvements in formerly used time-limitswitches of this type and an object of the invention is to procure atime-limit switch, in which the movement 5 necessary for opening andclosing the contacts in a simple and eliicient way is obtained by thedirect use of such variations of the length of the thermostat itself,which are due to variations of the temperature. Formerly 0 suchvariations of length have been designed to move the contactelement bymeans of a system of levers, but according to this invention themechanism for moving the contacts in accordance with the lengthvariations simply consists in the thermostat itself, one

end of which for this object being provided with necessary contactpieces.

The invention consists in certain parts, improvements and combinationshereinafter described, and more specifically pointed out in the claimshereunto appended.

In the accompanying drawings, which constitute a part of thisspecification, an embodiment of my invention is principally set forth. Fig. 1 shows a front view of the apparatus, the cover heilig removed inorder to show the electrical connections. Fig. 2 shows a longitudinalsection. The elongating element of the thermostat consists of a rod 1arranged as shown inside a tube 3 and surrounded by a coil 2, insulatedfrom both the rod and the tube. The lower end of the rod is connected tothe tube by means of an insulating support 4k and nuts 5. The rod andthe tube are preferably made of the same metal and the latter isprovided with contacts 6, 7, each mounted on a spring 61. The movementof said springs outwardly from the tube is limited by means of stophooks 71. At the upper part of the thermostat the rod 1 by means of nutsl1 is connected to a fixed strap 9, the tube 3 being pivotally connectedto said strap by means of a pin 8 as shown on the side of the centreline of thek rod. To the tube 3 there is rigidly connected an arm 10,the free endof which is pressed down by a spring 12, the force of thespring tending to turn the lower end of the tube to the right of Fig. 1.

In the position of the parts shown in the drawing the contact 6 is incontact with a contact member 13 arranged on the contact fixture 14.Directly above these contacts 6, 13 there is a coil 18 having an ironcore 19 for arc-blow-out when opening the circuit 20. This circuit 20 isconducted through the coil 2 around rod 1, said coil being connected inseries with coil 18. The contact 7 co-acts with another contact 21,fixed on a screw 22 arranged on a fixture 23. Said screw 22 against theaction of a spring 221 may be ad]usted by means of the insulating knob24. The main circuit 20-25 also comprises a condenser for arc-blow-outwhen opening` contacts 7, 21. The contact fixture 23 is c-onnected ktothe main circuit -25, which con tains the lamps 26. Both circuits 20,20-25 are connected to the battery 27, said battery by means of pin 8and tube 3 being in electrical connection with contacts 6, 7. lV hen theheating circuit 2() of the thermostat is closed by means of one of theswitches 28, the coil 2 receives an impulse of current, causing rod 1 tobecome quickly heated, owing to which the rod will become elongatedinstantly. This will cause the lower part of the thermostat to swing tothe right, thereby closing contacts 7, 21 and the main circuit 20-25,containing the lamps 26. The initial part of said movement of thethermostat to the right causes the circuit 20 to be opened. The heattioing also causes elongation of tube 3, but as the rod is situated insideot the Whole Construction, the elongating of the same will dominate, andat the same time the subsequent cooling et the rod will be retarded,thus causing the circuit or" the lamps to remain closed during' acertain space ottime. By the coolii 'i' corni-action ot the rod thespring l2 is stretched out and the lower part of tube 3 :avung bach tothe lett to such a degree, that spring G1 on the right side ceased totliei"eb \v causing contact T to leave contact 2l. rl`he lamp circuit isthen opened and shortl;T afterwards the contacts, (i, 13 become closedand the apparatus may be ready for another operation as described above.The space et time during which contacts T, 2l remain clos-ed andconsequently the lamjs ivill continue to giov', may bcontrolled byoperating the screvv 22. The tube 3 acts as a screen preventing' the.heat rays emanating trom rod l. from escaping to the outside, a featurevwhich will serve a constant resistance o the cooling of the rod.

It by means of screw 22 the contact fixture is moved to the lett, theact-ion ot' spring d1 will increase, thereby also increasing theilluminating time, as the thermostat may be adjusted to swing at aconstant angle when heated bf: Vthe current. The plate 29, upon whichthe thermostat is mounted and the cover 30 are both made of aninsulating ma terial, for instance bakelite. The cover 30 is attached tothe apparatus bj.' means of a screw 16.

Various moditications may be made Without departing from the spirit andscope. of this invf'ention, which is not to be limited to the particulardetails shown and described.

Having thus described the nature of our invention. vvhat we claim asnew, and desire to secure bv letters Patent, is-

l. In a timelimit switch, in combination, thermostat, a metal tubesurrounding said thermostat, means Jfor connecting one end o said metaltube to one end of said thermostat, contact pieces secured to said endof said metal tuber` contact piece co-acting With one ot said contactpieces tor closing an electric circuit for heating said thermostat andopening the same when the thermostat is heated, another contact piececo-acting with the other of said contact pieces for closing an electriccircuit for lighting a s vstem of lamps ivhen said heating circuit isopened, and means tor pivotally connecting said metal tube to a linedpin.

2. ln a time-limit switch, in combination, a thermostat, a pivotedmember disposed in parallel relation to said thermostat and having oneentr connected to one end ot the thermostat, contact pieces secured tosaid end of said member, a contact piece co-acting with one ot saidcontact pieces tor closing an electric circuit for heating saidthermostat and opening the same when the thermostat is heated, andanother contact piece co-acting with the other of said first contactpieces for closing an electric circuit lor lighting a system of lampswhen said heating circuit is opened.

3. In a time-limit switch, in combination, a thermostat, a pivotedmember disposed in parallel relation to said thermostat and having oneend connected to one end of the ther niostat, contact members flexiblysupported en said member at opposite sides thereof, a contact memberadapted to cooperate with one of said contact members for closing anelectric circuit through said thermostat thereby to heat the same, and asecond contact member adapted to cooperate `with the other flexiblysupported contact member for closing a circuit through a lightingsystem, said last coo}.:erating c ntact member being adjustable relativeto its cooperating member.

ln testimo v whereof we have signed our names to this specification.

KARL EINAR RUPERT LFGREN. ERIK ARTUR FAGERLUND.

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